As known to those skilled in the art, the knee is one of the most used and abused joints in the body. An individual uses the knee joint over one million times per year. As a result of such use, the knee is one of the most injured joints in the body. The knee is more vulnerable to injury because it is one of the most mobile and flexible joints. The more mobile a joint, the less stable the joint; thus, the more vulnerable the joint is to injury.
The knee is not only the largest joint in the body, but is also one of the most complex. The knee joint is comprised of four bones—the femur, tibia, fibula, and patella—that provide smooth, stable motion. The femur or thighbone is the large bone in the thigh. The tibia or shinbone is the large shinbone. The fibula is the small shinbone located next to the tibia. The patella or kneecap is the small bone in the front portion of the knee. Muscles, ligaments, and tendons connect all four of the above referenced bones.
The four bones of the knee joint are enclosed in a joint capsule lined with a special tissue called synovium, which produces a thick liquid called synovial fluid. The synovial fluid lubricates, protects, and nourishes the joint. The knee is kept in alignment by ligaments and tendons. The ligaments connect the bones and provide stability to joints. There are four main ligaments in the knee joint—anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and lateral collateral ligament (LCL).
The ACL and PCL are paired ligaments located in the center of the knee where the ACL crosses in front of the PCL. Thus, the ACL and PCL are referred to as the cruciate ligaments. The ACL and PCL prevent the tibia from moving forward and backward on the femur. The ACL originates near the back or posterior aspect of the thighbone and ends at the front or anterior aspect of the knee. In contrast, the PCL starts from the front or anterior aspect of the thighbone and ends at the back or posterior aspect of the knee.
The MCL is located on the inner or medial aspect of the knee and the LCL is located on the outer or lateral aspect of the knee. The MCL and LCL are also referred to as the collateral ligaments. The MCL and LCL supply stability when the knee moves from side to side or when an individual makes any sharp cutting moves.
Two semicircular rings of cartilage called menisci are located between the femur and tibia. Menisci supply additional stability to the knee when the knee twists or pivots. The inside or medial meniscus is also partially attached to the MCL. Accordingly, injury to the MCL leads to injury of the medial menisci, and vice versa. In contrast to the medial aspect of the knee, the outside or lateral meniscus is not attached to the collateral ligaments. Thus, injury to the MCL rarely leads to injury of the lateral meniscus and vice versa.
The knee also includes the patellar tendon and the quadriceps tendon. These tendons are connected to the patella. The patellar tendon—located below the patella—is a ropelike structure that connects the bottom of the patella to the top of the tibia. The quadriceps tendon is located above the patella. The quadriceps muscles straighten the knee by pulling at the patellar tendon via the patella. One of the quadriceps muscles, the vastus medialis, pulls the patella inward (i.e., medially). Another quadriceps muscle, the vastus lateralis, pulls the patella outward (i.e., laterally). Ligaments on the medial and lateral sides of the patella work with the quadriceps muscles to help keep the patella from moving out of a groove in the femur that is referred to as the femoral trochlea or trochlear groove.
The patella slides up and down in the groove as the knee bends and straightens. The patella has a smooth coating (i.e., articular cartilage) on its underside that permits the patella to slide easily in this groove. The trochlear groove is also coated with articular cartilage. Movement of the patella outside of trochlear groove can result in a subluxation when the patella moves partially out of and back into the groove, or a total patellar dislocation when the patella moves completely out of the groove and remains so.
Patellar subluxations are referred to as mild dislocations. Typically, the patella dislocates or subluxes laterally. The medial patellar ligament and the vastus medialis oblique muscle are important structures in preventing the patella from subluxing or dislocating laterally. When the patella subluxes or dislocates laterally, the medial patellar ligament and the vastus medialis muscle are usually damaged. One or more patellar subluxations or dislocations may cause the knee to feel unstable. This type of problem is referred to as patellar instability. This instability occurs because the muscles and ligaments are unable to keep the patella in the trochlear groove. Dislocation is the most severe form of patellar instability. Thus there is a need for a support brace that is capable of stabilizing patellar movement and restricting movement of the patella out of the trochlear groove.
Patellar dislocation may be classified as traumatic or atraumatic. Traumatic patellar dislocation is typically caused by an accident (e.g., a sudden twisting of the knee caused the patella to move out of the groove. In these cases, a ligament is typically torn and may never properly heal, thus leading to recurring knee problems.
Atraumatic patellar dislocation refers to the situation where there was no specific injury before the patella began moving out of the groove. Atraumatic patellar dislocation is common in individuals that are “loose-jointed.” It is also common in individuals having a misaligned patella (i.e., tilted or shifted) that places them at risk for instability.
Initially, individuals who dislocate their patella complain of sudden pain in their knee after a plant and twist type of injury or after a contact injury. Straightening the knee will oftentimes cause the patella to move back into the trochlear groove. Nevertheless, if the patella remains out of the groove, a specialist is often required to reposition it in the groove.
Patellar instability does not always lead to subluxation or dislocation. In situations where the kneecap shifts, but never actually dislocates, the condition can be limited to pain around the kneecap. Those skilled in the art refer to this condition as “excess lateral pressure syndrome” or “lateral tracking.” This type of pain typically occurs on the outside of the patella. Therefore, it is desirable to provide a support brace that facilitates proper tracking of the patella in the patellofemoral joint to thereby alleviate pain caused by improper tracking.
Patellofemoral pain can occur in one or both knees and is one of the most common causes of knee pain. Patellofemoral pain typically occurs in the front of the knee and occurs when the patella is compressed against the trochlear groove. The compression forces increase the further the knee is bent, resulting in an increase in pain. Therefore, activities that involve repetitive bending of the knee increase patellofemoral pain. Pain is often felt by the individual when moving up or down stairs or after sitting for long periods of time. Patellofemoral pain may also be accompanied by “clicking” and “grinding” or by a feeling that the knee “catches” in the patellofemoral joint. Thus, it is further desirable to provide a support brace that stabilizes movement of the patella in the patellofemoral joint, while permitting flexion of the knee during physical activities such as basketball or football.
Patellofemoral pain describes the location of the pain but not its cause. Overuse or previous injury to the knee is a common cause of patellofemoral pain. Biomechanical factors such as poor tracking of the patella in the trochlear groove, pronated feet, weak inner thigh muscles, and tight outer thigh muscles or ligaments can also cause patellofemoral pain. Common “wear and tear arthritis” (i.e., osteoarthritis) or damage to the articular cartilage (i.e., chondromalacia) on the back of the patella is another common cause of pain. Those suffering from patellofemoral pain often resort to knee support braces to prevent improper tracking of the patella and to alleviate the associated pain.
Bracing centralizes the patella in the trochlear groove such that it tracks more centrally, thereby decreasing pain. As mentioned above, the patella usually subluxes or dislocates laterally. Thus, most braces include a buttress positioned laterally to push the patella medially. Nevertheless, the patella may also sublux or dislocate medially. Thus it is desirable to provide a support brace having a buttress that is capable of applying sufficient lateral or medial forces against either knee to ensure proper tracking of the patella in the patellofemoral joint.
Patellar stabilizing braces are designed to reduce knee instability following a patellar dislocation or subluxation. They are usually recommended for twisting, pivoting, cutting, or jumping activities. In addition to providing increased stability to the patella, patellar stabilizing braces may also decrease the risk of injuring other parts of the knee. Thus, it is desirable to provide a support brace having a buttress that is capable of applying sufficient forces against the knee to ensure proper tracking of the patella in the patellofemoral joint.
Known braces provide at least one member (e.g., strap or buttress) for applying force against the knee, and specifically, the patella. The known buttresses, however, tend to shift during physical activities as a result of the relatively small areas of attachment to the brace body (i.e., relatively small attachment points provided by elongate arms). Thus it is desirable to provide a brace having a buttress that is secured in position by a second member (e.g., sheet-like member) that overlies at least a portion of the buttress and provides additional points of attachment to the brace body, thereby providing greater stability to the buttress.
Know braces also have a tendency to shift when the user applies tension to the buttress prior to attachment to the brace body. Therefore it is desirable to provide a brace having a stabilizing member for the user to grasp when applying tension to the buttress or additional tensioning members, to thereby secure the position of the brace and buttress relative to the knee when extending the brace against the knee.